The overall objective of the research described in this proposal is a complete description of ontogenetic development of the synaptic organization of certain mammalian and amphibian retinas. Included in such a description will be the degree of synaptic interconnection as a function of developmental stage; the factors which initiate or control developmental sequences; functional correlates of observed anatomical changes; and unifying principles discernible in amphibian and mammalian visual systems. This proposal will deal primarily with the retina and its plexiform layers. Emphasis will be placed upon quantitative morphological aspects of developing neuron sets.